Field of the Invention
The present invention relates to a display apparatus such as a liquid crystal display apparatus.
Description of the Background Art
Display apparatuses including a touch sensor, which has an input function by a touch operation, located on a display surface thereof have often been used. Projected capacitive (PCAP) touch panels include a conductive film located on a transparent substrate and include a technique for detecting a change in capacitance formed in the conductive film. The touch panels are formed by bonding two substrates together after a conductive film is formed on each of the two substrates, by forming conductive films opposed to each other on both sides of one substrate, or by forming a conductive film in two layers on one side of one substrate.
The display apparatus having the input function by the touch operation can be obtained by bonding the touch panel to the liquid crystal display apparatus or the like, but the display apparatus has a great thickness, which needs to be reduced.
To fill the need, an on-cell structure in which a sensor pattern formed of the conductive film is directly located on liquid crystal cells of the liquid crystal display apparatus and a polarizing film is bonded outside the sensor pattern has been examined (Japanese Patent Application Laid-Open No. 10-171599 (1998)).
A transparent conductive film has mainly been used as a material for a sensor pattern in a touch panel. The touch panel for a large display apparatus needs to have a reduced resistance of sensor wiring, so that application of metal wiring has been examined (Japanese Patent Application Laid-Open No. 2010-277392 and Japanese Patent Application Laid-Open No. 2010-097536).
However, when the touch panel formed of the metal wiring has the on-cell structure, a polarization axis of light near the metal wiring is projected onto another axis due to the influence by the metal wiring. As a result, a light control state that needs to be controlled in the polarizing film changes. Particularly when polarized light perpendicular to the polarization axis of the polarizing film is projected onto another axis, part of the light that needs to be blocked under normal circumstances is allowed to pass. This causes black floating (phenomenon in which a black area of an image turns whitish), thereby reducing contrast.
The introduction of the sensor pattern of the metal wiring makes it difficult to simultaneously optimize the polarization axis of the polarizing filter set by viewing angle properties of an LCD and a polarizing direction of an edge of the sensor pattern set to prevent moiré of the sensor. Consequently, for the application of the on-cell structure to reduce the thickness of the display apparatus, the intensity of black increases due to the formation of the wiring pattern misaligned from the polarization axis of the polarizing filter, thereby reducing the contrast.
The problems do not occur only in the touch panel, and may similarly occur in, for example, an array substrate or a counter substrate of the liquid crystal display apparatus having patterns through which visible light is not allowed to pass, such as wiring including a metal film and a black matrix.